From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E8B374302FF for ; Tue, 21 Jul 2026 07:34:05 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784619247; cv=none; b=Ivt539ucUSLjMGKzZ5lDR7XVel6sRzxMSywdc6s2wHXoNXgRFC2BmnHUzcp5p2MfHGUGPm2qkGo38krjO5SIma9YuZte1lMC2quYHDO1a4pq8u2remtcZLqmhlY8v9uizWGI9sUfYOuv2fUe47QP6hQV+m+iww5SEk3/DnUetpQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784619247; c=relaxed/simple; bh=uPh+tmeDSSYlx/ioV5qisYyld1D6uYREd/8c/Cb5pqQ=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=IGcUjoqoIL3fQWiPhyr+u+WAh78x0z8+OC7G9sdEm0+0Bv6eaBd+FaekbncIoru/mmfKeLW+tDhXlxA0wxGD84+oq9PG+s/yk4Pvf3Kn62fkEsMlDd0OVxcAe1r2rapvjWylHL6BOMt5RdYieYj0JUCj01jhUsoQJD5qQhjHsdY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=gn5uZuhU; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="gn5uZuhU" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 72D681F000E9; Tue, 21 Jul 2026 07:34:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1784619245; bh=3R7KAsu0U4XgVmb0eI5AipfVCOnfpS7yGck+kGJcP6c=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=gn5uZuhUpXzP9VigOESWPHGxXoZ5RZinv++4S35D7dxPQwaPB2DJAqvIz7cSnT7GA 4LgPXNxYrhRNw6829RNDPTllKQz+pCYGK3D4bqmtJWqNNobD+XSRmS2GT8nVB/fQJ+ SpPBFKeIKyfbfHSzTASJp1DxuRpYyp9Ln0XQh5cafRg9/SO7i2bLMSAPOPXuuGVDS7 2yj5q9Qamzuhz9BgwLuE90A9knKqMBMtwxivdKcqW0DP8RyAvaRIWJHzKm/4aMFewh 4kGyEqwghU9lKYEYw3ZYtRMgwHrAs+YoxZg2bfGxDGEKmiP3ZEjmmm7nOsQZPza84F siW62n/ym6rSA== Message-ID: <01ea11f8-65b4-4941-adf7-423c3f000292@kernel.org> Date: Tue, 21 Jul 2026 09:34:01 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3] mm/slub: prevent pfmemalloc objects from entering the barn To: hu.shengming@zte.com.cn, harry@kernel.org, akpm@linux-foundation.org Cc: hao.li@linux.dev, cl@gentwo.org, rientjes@google.com, roman.gushchin@linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org, zhang.run@zte.com.cn, cai.qu@zte.com.cn References: <20260721084522552ZPa16p1SRj3PYat3sqxuN@zte.com.cn> From: "Vlastimil Babka (SUSE)" Content-Language: en-US Autocrypt: addr=vbabka@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 8bit On 7/21/26 02:45, hu.shengming@zte.com.cn wrote: > From: Shengming Hu > > kmem_cache_return_sheaf() may refill a partially consumed sheaf before > placing it in the barn. Without an explicit restriction, this refill may > draw objects from pfmemalloc slabs and consume emergency reserves. > > Add __GFP_NOMEMALLOC so that returned sheaves are refilled only from > non-pfmemalloc slabs. Also add __GFP_NOWARN, as suggested by Hao Li, > because this refill is a best-effort attempt and failure is acceptable. > If the refill fails, flush and free the sheaf instead. > > Fixes: 3c1ea5c5019f ("slab: sheaf prefilling for guaranteed allocations") Wonder if 1ce20c28eafd ("slab: handle pfmemalloc slabs properly with sheaves") is a better match. Until that commit we just didn't care, and it seems like this is a case that commit missed? > Cc: stable@vger.kernel.org > Signed-off-by: Shengming Hu > --- > Changes in v3: > - Replace “normal memory” with the more precise “non-pfmemalloc slabs”, > and add Fixes: and Cc: stable@vger.kernel.org, as suggested by Harry. > - Link to v2: https://lore.kernel.org/all/20260720211127124sYtTNbvsxCXN9_pDh-pwt@zte.com.cn/ > > Changes in v2: > - Add __GFP_NOWARN as suggested by Hao. > - Link to v1: https://lore.kernel.org/all/20260719113701797vZ3R8NxiqYt8dEfeUxtON@zte.com.cn/ > > --- > mm/slub.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/mm/slub.c b/mm/slub.c > index 53b4976d3831..357b7522c817 100644 > --- a/mm/slub.c > +++ b/mm/slub.c > @@ -5123,7 +5123,7 @@ void kmem_cache_return_sheaf(struct kmem_cache *s, gfp_t gfp, > * simply flush and free it. > */ > if (!barn || data_race(barn->nr_full) >= MAX_FULL_SHEAVES || > - refill_sheaf(s, sheaf, gfp)) { > + refill_sheaf(s, sheaf, gfp | __GFP_NOMEMALLOC | __GFP_NOWARN)) { > sheaf_flush_unused(s, sheaf); > free_empty_sheaf(s, sheaf); > return;